The present patent application claims the right of priority under 35U.S.C. xc2xa7119 (a)-(d) of German Patent Application No. 102 01 763.8, filed Jan. 18, 2002.
The invention relates to an acoustic shielding article for the shielding of sound sources, which may be used, for example, in conjunction with motor vehicle engines. The acoustic shielding article includes a shaped thermoplastic element and a metal inlay element, e.g., a metal sheet, that is fixedly joined to the shaped thermoplastic element by means of injection molding. The shaped thermoplastic element has a surface that faces the source of sound.
Acoustic requirements in respect of machines, such as vehicles, e.g., in a motor vehicle engine compartment, typically require sound insulation (or abatement) measures. Intake manifolds of, for example, motor vehicle engines, are sound emitters, especially in the area of the collectors. The acoustic power arising from, for example, an intake manifold, derives (i) on the one hand from deformations of the outer wall (vibrations, natural resonances)/structure-borne sound, and (ii) on the other hand from internal noises (passage of sound through the outer wall)/airborne noise of the intake manifold. It is typically necessary to absorb or deaden these noises to achieve adequate levels of noise or sound abatement. Acoustic covers are typically used, for example, in motor vehicles to insulate the sound emissions of the engine and equipment, to influence the noise radiation of the motor vehicle positively (i.e., to reduce sound emissions). To achieve an adequate level of sound abatement in an optimum manner, components having the following characteristics are generally required: rigidity, dimensional stability, high weight per unit area, accuracy of fit and high self-dampening.
Components of this type can then be used as housing components of noise emitters (e.g., intake manifolds of motor vehicle engines) and/or as acoustic covers (e.g., acoustic covers in the motor vehicle engine compartments).
At present, thick-walled metal components, such as intake manifolds, are sometimes used in those applications where sound or noise is generated. Closed-cell foams may be applied to plastic components as dampers. Plastic parts may be ribbed to increase rigidity. Additional covers, optionally with an additional insulating layer (e.g., integral foam or bitumen-based insulating mats) may be employed. So-called insulating mats may be glued on a component surface to increase the specific weight per unit area of the component wall.
Furthermore, so-called xe2x80x9ckissing (or contact) pointsxe2x80x9d may be provided (e.g., on intake manifolds) to stiffen vibrating walls by supporting them against one another. Disadvantages of the contact point technique include disturbances in the inner volume of the component, a reduction in the flow cross-section and an increased construction space. The wall thicknesses of plastic components are normally increased to increase the weight per unit area and the stiffness of the component. The disadvantages of increasing wall thicknesses include a more demanding and expensive material use of plastic. The approach of increasing wall thicknesses is also ineffective due to the comparatively small modulus of elasticity of plastic. Ribs may optionally be mounted on the component wall, but this approach is typically subject to the accompanying disadvantages as described above.
The object of the invention is to provide an acoustic shielding article for the shielding of sound sources, in particular on motor vehicle engines, that avoids the disadvantages of the known constructions and offers comparatively good acoustic shielding.
In accordance with the present invention, there is provided an acoustic shielding article (1) comprising:
(a) a shaped thermoplastic element (3), said shaped thermoplastic element having a surface (11) that faces a source of sound (14); and
(b) an inlay element (2) having substantially opposed first (17) and second (20) surfaces (e.g., having a two-dimensional shape, such as that of a sheet), at least one of said first (17) and second (20) surfaces of said inlay element (2) being fixedly joined to said shaped thermoplastic element (3), said inlay element (2) being fabricated from metal,
wherein said shaped thermoplastic element (3) is formed by means of molding thermoplastic material onto at least one of said first (17) and second (20) surfaces of said inlay element (2), thereby fixedly joining said inlay element (2) to said shaped thermoplastic element (3).
The features that characterize the present invention are pointed out with particularity in the claims, which are annexed to and form a part of this disclosure. These and other features of the invention, its operating advantages and the specific objects obtained by its use will be more fully understood from the following detailed description and accompanying drawings in which preferred embodiments of the invention are illustrated and described.
Unless otherwise indicated, all numbers or expressions, such as those expressing structural dimensions, quantities of ingredients, etc. used in the specification and claims are understood as modified in all instances by the term xe2x80x9cabout.xe2x80x9d